Self-assembly of d-penicillaminato M6M′8 (M = Niii, Pdii, Ptii; M′ = Cui, Agi) clusters and their organization into extended LaiiiM6M′8 supramolecular structures

Abstract

A series of chiral M₆M′₈ cluster compounds having twelve free carboxylate groups, [M₆M′₈(D-pen-N,S)₁₂X]⁵⁻ (M/M′/X = Pd^II/Ag^I/Cl⁻ ([1]⁵⁻), Pd^II/Ag^I/Br⁻ ([2]⁵⁻), Pd^II/Ag^I/I⁻ ([3]⁵⁻), Ni^II/Ag^I/Cl⁻ ([4]⁵⁻), Pt^II/Ag^I/Cl⁻ ([5]⁵⁻), Pd^II/Cu^I/Cl⁻ ([6]⁵⁻); D-H₂pen = D-penicillamine), in which six cis-[M(D-pen-N,S)₂]²⁻ square-planar units are bound to a [M′₈X]⁷⁺ cubic core through sulfur-bridges, was synthesized by the reactions of cis-[M(D-pen-N,S)₂]²⁻ with M′ in water in the presence of halide ions. These M₆M′₈ clusters readily reacted with La³⁺ in aqueous buffer to form La^III₂M₆M′₈ heterotrimetallic compounds, La₂[1](CH₃COO), La₂[2](CH₃COO), La₂[3](CH₃COO), La₂[4](CH₃COO), La₂[5](CH₃COO) and La₂[6]Cl, in which the M₆M′₈ cluster units are linked by La³⁺ ions through carboxylate groups in a 1 : 2 ratio. While the La^III₂M₆Ag^I₈ compounds derived from [1]⁵⁻, [2]⁵⁻, [3]⁵⁻, [4]⁵⁻ and [5]⁵⁻ have a 1D helix supramolecular structure with a right-handedness, the La^III₂Pd^II₆Cu^I₈ compound derived from [6]⁵⁻ has a 2D sheet-like structure with a triangular grid of the Pd^II₆Cu^I₈ cluster units. When aqueous HCl was added to the reaction solution of [6]⁵⁻ and La³⁺, another La^III₂Pd^II₆Cu^I₈ heterotrimetallic compound, La₂[6]Cl·HCl, in which the Pd^II₆Cu^I₈ cluster units are linked by La³⁺ ions to form a 2D structure with a rectangular grid, was produced. The solid-state structures of these La^III₂M₆M′₈ compounds, determined by single-crystal X-ray crystallography, along with the spectroscopic properties of the M₆M′₈ cluster compounds in solution, are described.